A Florida State University student is crediting library books — one on 14th-century English philosophy — for saving his life early Thursday when a gunman opened fire on the Tallahassee campus.

FSU student Jason Derfuss could have been killed inside Strozier Library if he hadn’t been carrying a book-filled backpack that miraculously acted like a bulletproof vest.

Gunman Myron May opened fire on the 21-year-old Derfuss, but bullets hit his backpack — and didn’t reach the student’s body.

“There is no way I should be alive,” the humanities student told NBC News. “Literally, those books saved my life.”

The 304-page book “John Wyclif (Great Medieval Thinkers)” took the brunt of May’s bullets.

Derfuss posted Facebook pictures of his shot-up “John Wyclif” and another book that took bullets for him.

When Derfuss first heard gunfire in the library, he wanted to believe it was a firecracker.

“I heard what was unmistakably a gunshot behind me, and initially I kind of tried to rationalize it as a firecracker, but I knew exactly what it was,” Derfuss told WESH-TV. “He gunned down another student right in front of me, about 50 feet away.”

Derfuss recounted the next terrifying moments when May turned to shoot him.

“He was about 5 feet from me, but he hit my books,” Derfuss wrote on Facebook about the shooter. “Books one minute earlier I had checked out of the library, books that should not have stopped the bullet. But they did.”

The student didn’t notice the shot-up books for hours.

“I learned this about 3 hours after it happened, I never thought to check my bag,” he wrote. “I assumed I wasn’t a target. I assumed I was fine.”

The student said he can only believe that higher powers had plans for him to walk out of the library alive.

“The truth is I was almost killed tonight and God intervened,” he wrote. “I know conceptually He can do all things, but to physically witness the impossible and to be surrounded by such grace is indescribable. To God be the glory, forever and ever, Amen.”